(a) Field of the Invention
The invention relates to a broadcasting system, particularly to a control circuit and related control method for controlling frequency resonance point of an antenna.
(b) Description of the Related Art
An FM/DAB (digital audio broadcasting)/SVB (digital video broadcasting) antenna needs a broad receiving bandwidth. For example, the bandwidth of FM is about 88 MHz-108 MHz, the bandwidth of DVB-T (European digital video broadcasting-Terrestrial) is about 177.5 MHz-226.5 MHz/474 MHz-858 MHz, and the bandwidth of DAB is about 1452 MHz-1491 MHz. Other antennas, such as WiMAX (Worldwide Interoperability for Microwave Access) and WLAN (Wireless Local Area Network) also have different receiving bandwidth.
Generally speaking, a prior single antenna cannot support such a Broad receiving bandwidth to include many kinds of broadcasting signals at the same time. If a plurality of antennas and a plurality of tuning units are used to receive different broadcasting signals separately to support a broad bandwidth, the total volume as well as the hardware cost are increased.
If an integrated antenna can receive a plurality of different broadcasting signals, such as an antenna integrating in-car broadcasting reception and wireless communication network, the production cost of the integrated antenna can be obviously reduced. However, such an integrated antenna may receive unnecessary signals due to its broad bandwidth to thereby result in difficulty in post-processing. Besides, how to control such an integrated antenna to receive a desired signal and achieve better reception quality is an important task to endeavor.